A few years ago myself and a neighbor used to go horseback riding in the desert. One day while riding my wifes horse, he stumbled across a small wash (a dry river here in Az). It was maybe 2 ft across and 8-10" deep, he went down on his front knees so I let him have his head and he got up. No big deal, he was fine. I started laughing and told him he needed to watch where he put his feet and to pay attention to where we are going. Trust me horses are great to talk to and listen very well.
About a hundred yards or so further down the trail I heard a dirt bike behind us so I stood up in the stirrups and looked behind us to see if it was coming our way. Well just then I heard a whack and felt this sharp pain in my leg I fell back in the saddle and looked at my leg. This big piece of cholla cactus was sticking out of my leg. My wifes horse looked at me like "you need to watch where you put your feet and to pay attention to where we are going".
My neighbor started laughing and said "way to go Cactus Bob". So I use it online.
That will teach me to laugh at a horse.

for those that dont know what a cholla is. Look at the second picture. http://www.desertusa.com/mag99/may/papr/chollas.html

Bob